Put down the doughnut: Trans fat may hurt your memory

By Jen Christensen, CNN

Updated 10:14 AM ET, Wed November 26, 2014

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Photos:The history of trans fat

The Food and Drug Administration recently took a step toward eliminating most trans fat from our food. The government agency said it has made a preliminary determination that a major source of trans fats -- partially hydrogenated oils -- is no longer "generally recognized as safe." If the FDA's decision is finalized, partially hydrogenated oils will become food additives that could no longer be used without approval.

Ironically, Paul Sabatier won the 1912 Nobel Prize in Chemistry for discovering the hydrogenation method that activists are fighting to remove from our food processes today. His research detailed the way nickel could be used as a catalyst to create chemical reactions between hydrogen molecules and other compounds. This laid the groundwork for the creation of hydrogenated oils.

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Photos:The history of trans fat

How would you like to be known as the scientist who discovered "fat hardening"? Wilhelm Normann was awarded a patent in 1903 for the "Process for the Conversion of Unsaturated Fatty Acids or Their Glycerides into Saturated Compounds." Basically, Normann figured out how to turn liquid oils into a thicker, firmer substance through hydrogenation. This solid fat was less likely to spoil and cheaper to produce and transport.

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Photos:The history of trans fat

Procter & Gamble introduced Crisco to consumers in 1911 to "provide an economical alternative to animal fats and butter." The vegetable shortening was the first manufactured food product to contain trans fat.

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Photos:The history of trans fat

The Kaltman family tries to sell as much butter as possible at their New York dairy store in 1943 before a government deadline to freeze sales. During World War II, the federal government rationed butter in an attempt to control supply and demand while manufacturing plants were being used to support the war effort. As a result, margarine, which contains trans fat, grew in popularity.

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Photos:The history of trans fat

In 1957, the American Heart Association started encouraging people to limit fat in their diets in an effort to lower the risk of heart disease.

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Photos:The history of trans fat

As the popularity of fast-food restaurants grew, so did Americans' consumption of fat, calories and salt. In 1984, advocacy groups started campaigning to get saturated fat removed from fast-food chains. As a result, more restaurants began using partially hydrogenated oils that contained trans fat.

In 2004, Denmark made it illegal (PDF) for any food to have more than 2% trans fats. Offenders can face hefty fines or even prison terms. Other countries are also working to reduce trans fat in the food supply. Policies in Brazil, Costa Rica, the Netherlands and South Korea have proved effective over the past two decades, the World Health Organization says. The WHO has called for eliminating trans fat from the global food supply.

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Photos:The history of trans fat

In 2006, the FDA implemented a rule requiring manufacturers to list trans fat on nutrition labels. Under current regulations, companies can claim that their food has zero grams of trans fat if the it contains less than 0.5 grams of trans fat per serving. Consumers can check the ingredient list for "partially hydrogenated oil" to see whether there is a small amount of trans fat present.

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Photos:The history of trans fat

In 2007, New York became the first city to ban the use of partially hydrogenated vegetable oils and spreads in restaurants. A five-year follow-up study showed that the average trans fat content of New York customers' meals dropped from about 3 grams to 0.5 grams. The ban encouraged food companies across the country to remove trans fat from their products.

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Photos:The history of trans fat

Even state fairs jumped on board, many asking vendors to cook summer favorites -- like these deep-fried Milky Ways at the Indiana State Fair -- in trans fat-free oils.

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Photos:The history of trans fat

In 2012, first lady Michelle Obama and Agriculture Secretary Tom Vilsack announced guidelines for school lunches that will implement calorie caps and severely limit trans fat. Trans fat intake among American consumers has decreased from 4.6 grams per day in 2003 to about a gram a day in 2012, according to the FDA. However, "current intake remains a significant public health concern," FDA Commissioner Margaret Hamburg said this week in a written statement.

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Story highlights

A study of 1,000 working-age men found those with high-trans-fat diets remembered less

For every extra gram of trans fat the men ate a day, they remembered .76 fewer words

Scientists speculate that trans fat may cause a kind of cell damage that impacts memory

If you can't remember where your car keys are, you may want to eat fewer muffins.

It turns out the more trans fat you eat, the less you may remember, according to a study presented at the American Heart Association's scientific conference last week. Maybe that explains why some people don't know how they pack on the pounds over the holidays.

To look at what role trans fat played in memory, scientists in this new study looked at the diets of about 1,000 working-age healthy men.

The participants were shown 104 cards with words on them. With each new card the adult was shown, he was asked whether the word was new or had been repeated.

Examining their blood, scientists discovered that a disproportionate number of people who had a lot of trans fat in their system remembered fewer words than those with less in their system.

For each extra gram of trans fat eaten a day, the person in the study remembered .76 fewer words. The men who ate the most trans fat in the study remembered a total of about 10% fewer words compared with the adults who ate the least amount of trans fat, even when filtered for demographic qualities that typically affect one's memory like age, depression and education.

This is not the first study to show a link between memory problems and high-fat diets, but it is one of the first to look at this large a group of younger adult men. A 2012 study of older women found those who consumed more fat of all types had memory challenges. A 2013 study in the UK found similar results in a small number of young women.

However, it is still unclear what the direct connection is between trans fat and memory. A study like this can't prove cause and effect, but the researchers speculate one reason for the results may be that consuming large quantities of trans fat may cause oxidative stress, a kind of cell damage.

Dr. Olivia Okereke, an assistant professor of psychiatry at Harvard Medical School, has studied this issue with an older female population and thinks the oxidative stress theory is plausible. She also wonders whether there were other factors in the men's lives that lead to memory problems.

"Many of the men consuming the highest amounts of trans fat may also be the ones with the least healthy lifestyles or with the highest prevalence of health problems," she said.

Because of the obesity epidemic, there has been a concerted effort by doctors and the federal government to get trans fat out of American diets.

The American Heart Association advises Americans to eat no more than 2 grams of trans fat a day. That is what would naturally be found in the meat and dairy people typically eat. The dietary problems generally start when people eat a lot of processed foods.

Manufacturers started using trans fat to length the amount of time food could sit on a shelf, processed food in particular.

In 2006, the FDA required manufacturers to list the amount of trans fat on nutrition labels. That requirement caused many companies to reduce the trans fat from their products ... at least some of it. The law still allows companies to list products as "trans fat free" even if they have 0.5 grams of fat.

"From a health standpoint, trans fat consumption has been linked to higher body weight, more aggression and heart disease," study author Dr. Beatrice Golomb said. She often warns patients against eating a diet rich in trans fats. "As I tell patients, while trans fats increase the shelf life of foods, they reduce the shelf life of patients."